HydroLearn is an education project funded by the National Science Foundation to promote the collaborative development and adoption of active-learning resources in hydrology and water resources engineering. Using the HydroLearn platform, instructors can: Explore existing courses, case studies, and learning activities and use in classrooms, Customize existing courses and learning activities, or build new ones, Share back learning resources for instructors to use, Get guidance on how to develop effective learning outcomes and assessment rubrics. HydroLearn is freely accessible to everyone, but primarily designed for instructors and students including instructors who want to develop, customize and share innovative learning resources in hydrology and water resources and students who want to learn about fundamental and emerging topics in hydrology and water resources engineering using active learning approaches. HydroLearn aims to create a community of users who are interested in adopting innovative active-learning resources in hydrology and water resources engineering. By providing educators with a mechanism for contribution, customization and sharing of educational content, HydroLearn aspires to alleviate existing development and adoption barriers to encourage educators to engage in active-learning innovations. HydroLearn also aims to propagate good pedagogical practices by providing instructors with support on how to develop sound and effective learning activities, learning outcomes and assessment rubrics.